1. Field of the Invention
The invention relates to an ink supply system as well as to a process for cleaning this type of ink supply system.
2. The Prior Art
Ink supply systems already exist for inkjet printers, which have a print head assembly with at least one print head. As per EP 1 831 025 B1, this form of system comprises a supply tank which contains an ink reservoir for an inkjet print head and a return tank which has an overflow for ink unused by the inkjet print head. An intermediate container, which contains a larger reservoir of ink is connected with the supply tank via a line with interconnected filter assembly. Depending on the level of ink in the supply tank, a means of conveyance transports ink from the intermediate container into the supply tank. From the supply tank, the ink is fed via a supply line through the first connection line of a flow channel in a print head, whereby the second connection line for this flow channel is connected with the return tank via an additional connection line, which is linked with the intermediate container by means of an additional connection line with interconnected filter assembly and means of conveyance. During printing, a means such as a vacuum generator generates an internal differential pressure between the inside of the supply tank and the inside of the return tank, such that this pressure differential transports the ink from the supply tank through the print head to the return tank. In addition to supplying the ink to the print head or print heads, it is also already known that the print head is flushed through with this form of inkjet printing system, in order to remove any impurities. In order to do so a positive pressure is generated in the supply tank and the return tank, which ensures that the ink contained in the two tanks is flushed through the print head. The disadvantage of this system is that flushing the ink through the fine drilled holes in the individual inkjet nozzles of the inkjet print head forces the deposited impurities in the system through the fine nozzles apertures of the individual print head nozzles and can block these.